With conventional push rods each push rod is constructed of a solid steel rod, sometimes having a oil feed hole through the center feeding the rocker arm. Each push rod seats in a lifter, and the lifter body rides on one lobe of the camshaft, the other end pushes the rocker arm, allowing the valves to open and close. Fixed units open and close the valves only. Mechanical systems do one specific job, having no allowance of worn parts (as hydraulic valve lifters that remain at zero valve lash). Push rods are designed to follow the cam and lifter characteristics, solid lifters maintain a fixed adjusted lash setting which remain inflexable, a wide lash setting causes wear over that of a hydraulic lifter being fed under oil pressure which maintains a tight setting at all times allowing for wear and other variables. Many lifters are designed to trap oil in the body chamber and expand beyond its predetermined zero valve lash point, holding the valves open at high speeds causing valve float. However, with high performance cams the valves are timed to have considerable overlap and duration in order to provide for a large fuel flow through the engine. At low speeds this large overlap is not necessary and the engine runs inefficiently, resulting in a loss in low speed horsepower. Basically, increasing the valve lash will shorten valve duration and reduce overlap, increasing crankshaft rotating degrees in relationship to the valves. This results in an improvement in low speed performance. However, excessive lash causes considerable noise, wear and loss of horsepower at higher revolutions per minute (rpms).
The novel hydraulic valve timing push rod varies valve timing automatically, by increasing or widening valve lash at low speeds, improves low end torque horsepower, yet while engine speeds increase, the hydraulic push rod allows for expansion, decreasing valve lash, consequently lengthening valve duration and overlap, improving high speed performance.
Refer to the variable hydraulic valve lifter filed June 20, 1966, U.S. Pat. No. 3,304,925 by my late father James E. Rhoads and also another U.S. Pat. No. 3,921,609 filed Aug. 16, 1974, both being hydraulic variable valve lifters which work on the same principles, with a few exceptions being basically incorporated in a push rod and particularly having external aperture bleed adjustments, meticulously controlling the rate of bleed for valve delay.
The push rod herein described is designed to prove favorable characteristics over the other two patents which work basically on the same principle. The push rod having multiple favorability, number one the engine need not be majorly disassembled for installation, easy installation requires only the removal of valve covers and rocker arms, drop in device and reassemble, while lifter removal requires a more invalved disassembly for example pulling off the intake manifold and other involvements. Another benefit is the push rod may be placed in foreign car engines, not equipped for hydraulic valve lifters, a non manufactured item, they too can have a variable valve timing device that will result in a considerable horsepower increase, fuel economy and improving smog pollutant emissions.